Displaying publications 1 - 20 of 2561 in total

  1. = Ling OLH, Shahruddin Ahmad, Kadaruddin Aiyub, Yaakob Mohd Jani, Ting KH
    Sains Malaysiana, 2012;41:179-191.
    Air environmental health indicators were defined operationally as a combination of “air quality” and “air-related health” indicators. Clean air is a basic precondition of human health. Air pollutants had been identified with potential negative impact on health especially on respiratory and cardiovascular diseases. Thus, studies are necessary to identify and understand the state of environmental health. This study was aimed to examine and analyse the air environmental health condition in city of Kuala Lumpur by using a set of indicators. House to house questionnaire survey was carried out to collect air-related health data, and air quality sampling was carried out to identify ambient air quality level of the city. In general, city of Kuala Lumpur was found to have a “moderate level” of air quality. Air-related illnesses indicated by acute respiratory infection and asthma were found to be higher in more developed or higher density zones, as compared to other zones. Besides, air-related illnesses were significantly correlated to respondents’ exposure to air pollution. The findings imply that human health can be improved by managing the urban development and its environmental quality properly.
  2. A.I. Alsabery, H. Saleh, I. Hashim, A.J. Chamkha, B. Chanane
    Sains Malaysiana, 2017;46:803-815.
    The problem of Darcian natural convection in a trapezoidal cavity partly filled with porous layer and partly with nanofluid layer is studied numerically using finite difference method. The left slopping wall is maintained at a constant hot temperature and the right slopping wall is maintained at a constant cold temperature, while the horizontal walls are adiabatic. Water-based nanofluids with Ag or Cu or TiO2 nanoparticles are chosen for the investigation. The governing parameters of this study are the Rayleigh number (104 ≤ Ra ≤ 107), Darcy number (10–5 ≤ Da ≤ 10–3), nanoparticle volume fraction (0 ≤ φ ≤ 0.2), porous layer thickness (0.3 ≤ S ≤ 0,7), the side wall inclination angle (0° ≤ ϕ ≤ 21.8°) and the inclination angle of the cavity (0° ≤ ϖ ≤ 90°). Explanation for the influence of various above-mentioned parameters on streamlines, isotherms and overall heat transfer is provided on the basis of thermal conductivities of nanoparticles, water and porous medium. It is shown that convection increases remarkably by the addition of silver-water nanofluid and the heat transfer rate is affected by the inclination angle of the cavity variation. The results have possible applications in heat-removal and heat-storage fluid-saturated porous systems.
  3. A.K.M. Aminul Islam, Nurina Anuar, Zahira Yaakob, Jaharah A. Ghani
    Sains Malaysiana, 2015;44:1275-1281.
    The seeds of 6 × 6 half diallel progenies of Jatropha curcas were used to evaluate the effects of genotypes (parents and their hybrids) on germination traits of jatropha at Universiti Kebangsaan Malaysia. Germination traits were varied significantly (p<0.01) among the seeds of hybrids and their parents. The germination was started at four days after planting and prolonged until 15 days. Seed germination varied from 58.06 to 92.76% among the parents and 53.43 to 98.96% among the hybrids. The highest germination was observed in the hybrid P2 × P4 and none of the hybrid or parent showed complete (100%) germination. The maximum GI (germination index) and SVI (seedling vigour index) were found in the hybrids P1 × P5 and P1 × P2 and the lowest in P2 × P4 and P3 × P6, respectively. For most germination parameters parents behaved poorly than that of the hybrids.
  4. A.K.M. Aminul Islam, Nurina Anuar, Zahira Yaakob, Jaharah A. Ghani, Mohamad Osman
    Sains Malaysiana, 2015;44:979-986.
    Six parents (P1, P2, P3, P4, P5 and P6) half diallel population of Jatropha curcas were evaluated to determine the combining ability, genetic components of variance and heterosis for yield contributing traits. Diallel analysis showed that both additive and dominance gene action was responsible for the genetic regulation of all the traits under study. The cross combination P1 × P3 showed the highest positive specific combining ability for seed yield per plant. Combining ability results were also in close agreement with the findings of estimate of genetic components of variance. The seeds per fruit (89%) and 100-seed weight (93%) showed maximum narrow sense heritability. Seed yield per plant showed high mid parent (254.13%) and better parent (202.36%) heterosis in the cross combinations of P2 × P5 and P1 × P3, respectively.The parents of P1, P2, P3 and P5 were found to be superior for seed yield components when used in cross. Considering seed production for each plant, the hybrids P1 × P2, P1 × P3, P2 × P5 and P4 × P6 could be selected for the development of hybrid varieties.
  5. A.M. Sifullah, Y. Nukman, M.A. Hassan, A. Hossain, Khaled I. Ahmed
    Sains Malaysiana, 2017;46:755-762.
    Laser cutting is a non-traditional cutting process and cutting of square blank in stainless steel-304 sheets cause heat affected zone (HAZ) and thermal stress. Formation of HAZ is undesirable and excessive stress cause surface defects. Thus, it is necessary to analyze them intensively. The process of laser cutting is a complex thermo-mechanical process. Hence, in this study a thermo-mechanical finite element model has been introduced by ANSYS to predict the temporal variation together with thermal stress and width of heat affected zone (HAZ). CO2 laser is used to cut 10 × 10 mm square blank in a 3 mm thick stainless steel-304 sheet. Optical microscope and SEM are used to analyse the parametric effect on surface quality at the cutting edge. The results showed that maximum temperature at the cutting edge is about to melting temperature and independent to laser power and cutting speed. Importantly, cutting speed has significant effect on rate of temperature variation. Moreover, the width of HAZ increases with the increase of laser power and decrease of cutting speed. However results of ANOVA suggested that laser power is the most significant parameter having 64.21% of contribution to width of HAZ. Furthermore, maximum stress is observed at the corner; which is supported by SEM analysis.
  6. A.N. Fauzana, B.Z. Azmi, M.G.M. Sabri, W.R. Wan Abdullah, M. Hashim
    Sains Malaysiana, 2013;42:1139-1144.
    A small amount of MnO2 dopant was added to ZnO system to see the improvement of the ceramic varistor microstructural and nonlinear electrical properties. The samples were prepared using solid-state reaction method and the microstructure and nonlinear electrical properties of the ZnO-xMnO2 system were investigated for x = 0.011 to 0.026 mol%, at three sintering temperatures, 1180°C, 1240°C and 1300°C for 1 and 2 h sintering time. The XRD and EDAX analyses showed that the main phase was ZnO while ZnMnO3 and ZnMnO7 as the secondary phases developed and distributed at the grain boundaries and triple point junction. The SEM observation revealed that prolonged sintering temperature and time improved the microstructure uniformity and strongly influences the nonlinear behavior of the samples. The maximum density and grain size have been observed at 92% of theoretical density and 10.8 μm, respectively and occur at the highest sintering temperature which is 1300°C. The value of nonlinear coefficient α is found to increase with the increase of MnO2 doping level up to 0.016 mol% and drop with further doping level increment for all sintering temperatures and time.
  7. A.N. Yusoff
    Sains Malaysiana, 2013;42:765-771.
    Kajian pengimejan resonans magnet kefungsian (fMRI) subjek tunggal ini menyelidiki interaksi psikofisiologi (PPI) antara girus presentral (PCG) dan lobus parietal superior (SPL) kanan semasa tepikan jari rentak sendiri secara bilateral. Model kehubungan efektif antara PCG dan SPL kanan dibina menggunakan analisis PPI dengan mengambil daya dan laju tepikan sebagai faktor uji kaji. Keputusan menunjukkan bahawa peningkatan daya dan laju tepikan masing-masing mengaktifkan PCG bilateral dan SPL kanan secara bererti (p<0.05). PCG dan SPL kanan didapati saling berhubungan semasa tepikan jari dilakukan dengan daya dan laju tepikan sebagai faktor uji kaji yang mempengaruhi kehubungan efektif antara mereka. Kajian ini telah mendedahkan maklumat asas berguna untuk kajian fMRI pada masa depan ke atas koordinasi motor dan boleh digunakan untuk mengkaji ketaktertiban otak misalnya strok.
    Sains Malaysiana, 2013;42:1811-1814.
    We studied the clusters of GaAs by using the density functional theory simulation to optimize the structure. We determined the binding energy, bond lengths, Fermi energy and vibrational frequencies for all of the clusters. We use the Raman data of nanowires of GaAs to compare our calculated values with the experimental values of the vibrational frequencies. The nanowire of GaAs gives a Raman line at 256 cm-1 whereas in the bipyramidal Ga2As3 the calculated value is 256.33 cm-1. Similarly 285 cm-1 found in the experimental Raman data agrees with 286.21 cm-1 found in the values calculated for Ga2As2 (linear) showing that linear bonds occur in the nanowire. The GaAs is found in two structures zinc-blend as well as wurtzite structures. In the nanowire mixed structures as well as clusters are formed.
    Sains Malaysiana, 2013;42:1599-1603.
    Salted fish is a locally processed raw food which is used in everyday cooking among Malaysians. Previous studies suggested that salted fish intake was a risk of nasopharyngeal cancer. Hence, this study was carried out to evaluate gene mutation effects through the induction of mutagenic effect of aqueous and methanol extracts of salted fish from Balik Pulau, Pulau Pinang, Malaysia. Balik Pulau was chosen for sampling purpose due to its popularity as a commercial centre for local raw fisheries in Malaysia. Evaluation of mutagenic effect was carried out by hprt Gene Mutation Assay towards V79 lung fibroblast cells. It was found that the aqueous and methanol extracts of salted fish were not cytotoxic towards V79 lung fibroblast cells. It was also found that the extracts of salted fish from Balik Pulau were not mutagenic towards hprt gene of V79 lung fibroblast cells as the mutation frequency of the extracts did not exceed 3 times of the value for negative control mutation frequency. In conclusion, both aqueous and methanol extracts of salted fish from Balik Pulau did not have gene mutation effect towards hprt gene in vitro. However, other toxicological profile could be assessed to determine the mechanism of toxicity of salted fish.
    Sains Malaysiana, 2013;42:1727-1733.
    Invention of milling combined laser sintering system (MLSS) is able to reduce the mould manufacturing time and improve the mould accuracy. Thus, more study is needed to increase the understanding for the laser sintered material machining characteristic to gain benefit from the invention of MLSS. This paper clarified the analysis of laser sintered material machinability with the application of Finite Element Method (FEM). Mild steel AISI1055 was applied in developing the Finite Element model in this study due to its popularity in machinability test and adequate level of data availability. 2D orthogonal cutting was employed on edge design tools with updated Lagrangian coupled thermo mechanical plane strain model. Adaptive meshing, tool edge radius and various types of friction models were assigned to obtain efficient simulations and precise cutting results. Cutting force and cutting-edge temperature estimated by Finite Element Method are validated against corresponding experimental values by previous researchers. In the study, cutting force increases when radial depth increases and lowest error acquired when the shear friction factor of 0.8 was applied. Machining simulation for laser sintered materials estimated lower cutting force compared with mild steel AISI1055 due to lower Young modulus. Higher cutting temperature estimated for machining simulation laser sintered material compared with machining simulation mild steel AISI1055 due to its low thermal conductivity.
    Sains Malaysiana, 2013;42:1697-1705.
    The extraction of catfish (Clarias gariepinus) skin gelatin was optimized by using response surface methodology (RSM) employing a central composite design (CCD). RSM with 3-factors, 5-levels CCD was carried out for the optimization. The independent variables were suggested which include NaOH concentration (0.07-0.23 mol/L), acetic acid concentration (0.04-0.14 mol/L) and extraction temperature (40-80°C) with the percentage of hydroxyproline recovery (Y) as dependant variable. A maximum Y of 65.32% for gelatin processing was obtained using a combination of 0.13 mol/L NaOH and 0.09 mol/L acetic acid for 1 h, followed by a hot-water extraction at 64.92°C for 3 h. The results indicated a high protein content (88.46 g/100 g) in the extracted gelatin with a viscosity of 3.45 mPa.s, 286.71 g gel strength and 173 residues per 1000 residues of imino acids (proline and hydroxyproline). Furthermore, the gelatin from catfish also showed a relatively good instrumental texture quality according to texture profile analysis (TPA).
    Sains Malaysiana, 2013;42:1231-1235.
    An experiment was conducted to determine the effects of stocking density on growth performance and production of Amblypharyngodon mola during 9 July to 9 October, 2011. There were three treatments, each with three replications in nine earthen ponds with an average depth of 1.5 m. Ponds of three treatments T1, T2 and T3 were stocked with mola at the density of 145000; 73000 and 36500 ind. ha-1. Water temperature, transparency, total alkalinity, pH, dissolved oxygen, Nitrate-nitrogen, nitrite-nitrogen, ammonia-nitrogen, phosphate-phosphorus and chlorophyll-a of the ponds water were measured weekly. Among water quality parameters, significant differences (p<0.05) were observed in case of temperature and dissolved oxygen. The lowest PO4-P and chlorophyll-a concentration were observed in T1. All water quality parameters were in suitable range of fish culture. The numbers of fishes at harvest were 155633.31±11.5; 84200±4 and 45600±7.21 indi. ha-1 in T1, T2 and T3, respectively. The mean weight of mola during harvest decreased significantly (p<0.05) with increasing stocking density. The net production of mola was significantly higher in treatment T3 (43.22±8.66 kg ha-1) than T2 (34.82±6.53 kg ha-1) and T1 (32.74±6.53 kg ha-1). Considering the highest net production among the three tested densities, the stocking density applied in T3 was found the best.
    Sains Malaysiana, 2013;42:1663-1670.
    Filem nipis ZnO terdop Ga (ZnO:Ga) disediakan menggunakan teknik sol-gel dan salutan berputar. Ga didopkan kepada ZnO dengan peratusan berat (wt. %) yang berbeza iaitu 0, 2, 4, 6 dan 8 wt. %. Kesan pengedopan Ga ke atas struktur dan sifat optik filem nipis ZnO dikaji. Pencirian struktur filem nipis ini dilakukan menggunakan kaedah pembelauan sinar-X (XRD), mikroskop imbasan elektron pancaran medan (FESEM) dan mikroskop daya atom (AFM). Pencirian sifat optik filem nipis pula dilakukan menggunakan spektroskopi ultraungu cahaya nampak (UV-VIS) dan fotoluminesen (PL). Ujian XRD mengesahkan kesemua sampel berstruktur wurtzit. Saiz kristalit ZnO mengecil dengan peningkatan peratusan berat Ga seterusnya mengurangkan kekasaran permukaan filem. Pengedopan Ga menunjukkan peratus transmisi cahaya pada panjang gelombang 300 - 380 nm bertambah berbanding filem nipis ZnO tanpa dop. Nilai jurang tenaga optik, Eg dan keamatan PL filem nipis ZnO meningkat apabila pengedopan Ga dilakukan. Hasil kajian ini menunjukkan saiz kristalit yang lebih kecil memberi kesan ke atas sifat optik sampel pada peratus pengedopan Ga 0-6%. Pada peratus pengedopan Ga yang lebih tinggi, kesan transformasi struktur menjadi lebih dominan dalam mempengaruhi nilai Eg.
  14. AWIS SUKARNI MOHMAD SABERE, Zuriati Zakaria, Ismail B
    Sains Malaysiana, 2013;42:1581-1584.
    This study was conducted to investigate pesticide residues in paddy crops derived from two different types of cultivation, namely the cultural plot managed by the Malaysian Agriculture Research and Development Institute (MARDI) and the second from the farmers’ rice fields which did not follow schedules suggested by MARDI. Sample collection was carried out at post harvest. To determine the concentration of organochlorine pesticides, a gas chromatograph equipped with an electron capture detector (GC-ECD) was used. The range of pesticide residues in the leaf samples was from N/D to 579.60 ppb, in stem samples from N/D to 368.93 ppb and in the rice grain from N/D to 22.37 ppb. Some of the rice samples had levels that exceeded the standard MRL (as stipulated by WHO).
  15. Abbas Ali M, Bamalli Nouruddeen Z, Ida I. Muhamad, Abd Latip R, Hidayu Othman N
    Sains Malaysiana, 2014;43:1189-1195.
    The aim of this study was to evaluate on how heat treatments by microwave oven may affect the oxidative degradation of sunflower oil (SFO) and its blend with palm olein (Po). The blend was prepared in the volume ratio of 40:60 (Po: SFO, PSF). The samples were exposed to microwave heating at medium power setting, for different periods. In this study, refractive index, free fatty acid content, peroxide value, p-anisidine value, total oxidation (Tomx), specific extinction, viscosity, polymer content, polar compounds and food oil sensor value of the oils all increased, whereas iodine value and C 18:21C16:0 ratio decreased as microwave heating progressed. Microwave heating temperature increased with increasing heating time and longer heating times resulted in a greater degree of oil deterioration. The percentage of linoleic acid tended to decrease, whereas the percentage of palmitic acid increased. The effect of adding PO to SFO on the formation of free fatty acids and conjugated dienes during microwave treatment was not significant (p< 0.05). No significant differences in food oil sensor value was observed between SFO and PSF. Based on the most oxidative stability criteria, it can be concluded that the microwave heating caused the formation of comparatively lower amounts of oxidation products in PSF compared to SFO, indicating a lower extent of oxidative degradation of PSF.
  16. Abbas FM, Normah Mohd Noor, Elnur EE, AlGaali E, Zainon Mohd Ali, Roohaida Othman
    The aim of this study was to establish an effective protocol for callus induction from the seed explants of Solanum dubium and to investigate the callus extract ability in milk clotting activity. The effects of growth regulator, basal media strength and sucrose were studied using different concentrations (0.5, 1.0, 1.5, and 2.0 mg/L) of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), naphthalene acetic acid (NAA) and 2,4-dichlorophenoxy-acetic acid (2,4-D) alone or in combination with 0.5 mg/L of 6-benzylamino purine (BAP). For milk clotting activity, about 50 or 100 μL extracts of seed callus was mixed with 2 mL 50% milk held at 55°C for 5 and 10 min until milk clotting occurred. The results showed that NAA alone or in combination with BAP gave a higher callusing percentage (80 to100%) compared to the other plant growth regulators at the same concentrations. When an auxin was supplied in combination with BAP, a significant increase in callusing percentage or degree of callusing was observed. The time required for callus to be developed was shortened and the quality of the induced callus improved. An increase in callus growth in low sucrose (10 g/L) concentration was found be comparable (88%) to high sucrose concentration (30 g/L; 60%). Crude extracts obtained from S. dubium callus were shown to exhibit milk clotting activity.
  17. Abd Rahim A, Hashim M, Ali N
    In this work we prepared germanium nanostructures by means of filling the material inside porous silicon (PS) using conventional and cost effective technique, thermal evaporator. The PS acts as patterned substrate. It was prepared by anodization of silicon wafer in ethanoic hydrofluoric acid (HF). A Ge layer was then deposited onto the PS by thermal evaporation. This was followed by deposition of Si layer by thermal evaporation and anneal at 650οC for 30 min. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400οC for 10 min to form metal semiconductor metal (MSM) photodetector. Structural analysis of the samples was performed using energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). EDX spectrum suggests the presence of Ge inside the pores structure. Raman spectrum showed that good crystalline structure of Ge can be produced inside silicon pores with a phase with the diamond structure by (111), (220) and (400) reflections. Finally current-voltage (I-V) measurement of the MSM photodetector was carried out and showed lower dark currents compared to that of Si control device. Interestingly the device showed enhanced current gain compared to Si device which can be associated with the presence of Ge nanostructures in the porous silicon.
  18. Abd Rahman Jabir Mohd Din, Shaharudin Abdul Razak, Sabaratnam V
    Sains Malaysiana, 2012;41:1197-1203.
    A feeding trial was conducted to investigate the effect of mushroom supplementation as a prebiotic compound in an insect-based diet on the growth performance and feed utilization of red Tilapia (Oreochromis sp.). A total of 120 fingerlings were divided in triplicates for each treatment. Four experimental diets were offered to the fishes within a 56 days treatment period. Out of the four diets, three contained mushroom stalk meal (MSM) supplementation at various levels of inclusion of prebiotic compound (0.5% MSM; 1.0% MSM; 1.5% MSM) and the fourth a control diet without MSM inclusion. During the growth test, fish receiving diet containing prebiotic showed significantly higher (p<0.05) mean individual body weight in comparison with the control diet. The best effect was obtained in fish fed with Diet 2, where the specific growth rate (SGR) was 1.74%, feed conversion ratio (FCR) was 0.58, protein efficiency ratio (PER) was 5.17 and survival was 93.33%. No significant differences (p>0.05) were observed in whole body protein and ash contents among the fish feeding on these diets. All water quality parameters showed no significant difference (p>0.05) in all treatments. The result of this feeding trial indicated that the 10% supplementation level of MSM as a prebiotic for tilapia could be used in the insect-based diet, Zophobas morio.
  19. Abd Rahni Mt Piah, Unsworth K
    Sains Malaysiana, 2011;40:1173-1178.
    In 2004, Wang and Tan described a rational Bernstein-Bézier curve interpolation scheme using a quartic numerator and linear denominator. The scheme has a unique representation, with parameters that can be used either to change the shape of the curve or to increase its smoothness. Sufficient conditions are derived by Wang and Tan for preserving monotonicity, and for achieving either C1 or C2 continuity. In this paper, improved sufficient conditions are given and some numerical results presented.
  20. Abd. Fatah Wahab, Jamaludin Md. Ali, Ahmad Abd. Majid, Abu Osman Md. Tap
    Pembinaan model geometri berbantukan komputer (CAGD) dengan titik data yang mempunyai ketakpastian adalah sukar dan mencabar. Dalam kertas ini, pembinaan model splin-B kabur sebagai perwakilan matematik bagi lengkung dengan data ketakpastian menggunakan titik kawalan kabur dan titik kawalan penyahkaburan dibincangkan. Lengkung splin-B kabur atau splin-B penyahkaburan kubik untuk masalah data ketakpastian akan diperihalkan dengan menggunakan kaedah penghampiran splin-B kubik yang ditakrif menerusi titik kawalan kabur dan titik kawalan penyahkaburan. Bagi menyelesaikan masalah mengenai titik data ketakpastian pula, kaedah pengkaburan dan penyahkaburan titik data berkomponen kabur (penyahkaburan) beserta modelnya diperkenalkan. Bagi menguji tahap keberkesanan model, beberapa contoh lengkung simulasi data tersebut juga dibincangkan.
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